A synthetic jet is generated by alternating momentary ejection and suction of a fluid across an orifice such that the net mass flux is zero. A typical configuration for a device used to generate a synthetic jet is to place a biomorph piezoelectric disk at the bottom of a cylinder. The cylinder includes a small orifice opposite the piezoelectric disk. The effect of the bending disk is to actuate like a piston head to generate ejection and suction through the orifice. In response to the motions, vortices are generated which propagate away from the orifice. The synthetic jet is formed when the vortices generated by the orifice coalesce to form a jet, in a time-averaged sense.
A synthetic jet actuator can be deployed in a flow control system. A unique feature of synthetic jets is that they are formed entirely from the working fluid of the flow system. Thus, the jets can be used to transfer linear momentum to the flow system without a net injection of mass.
Synthetic jets can be produced over a broad range of length and time-scales. Thus, synthetic jets have been proposed for a broad range of flow control applications. For example, synthetic jet actuators have been proposed as a mechanism for affecting flow separation over a wing. In addition, the synthetic jet actuators are also used as a mechanism for providing focused cooling.
In designing a mechanism for producing a synthetic jet, issues that are considered are the amount linear momentum that is produced per unit of weight of the mechanism and/or per unit power input for the mechanism. These ratios provide some measures of the efficiency of the device. For current synthetic jet designs, such as the piston design described above, the efficiency of the designs limit their applicability for weight and/or power sensitive applications, such as aircraft. In view of the above, new apparatus and methods for generating synthetic jet actuators are desired.